TS and VS were analyzed according to the standard method [15]. Water-insoluble VS (IVS) was determined after the sample was washed with distilled water for three times. The total organic carbon (TOC) was calculated using the relationship TOC = VS/1.8 [16]. The total Kjeldahl nitrogen (TKN) level was measured by a Foss Kjeldahl Analyzer (ZDDN-II, China) after digesting using a Foss Tecator. Soluble chemical oxygen demand (SCOD) was obtained after centrifugation and filtration through a 0.45-lm membrane and measured with a chemical oxygen demand analysis system (Lianhua technology, China). pH was measured by a pH meter (PHS-3C, China).